1. Technical Field
The present invention pertains to motion platform systems. In particular, the present invention pertains to a motion platform system for use in exercise or other equipment (e.g., various simulators, etc.) that rotates a motion platform structure via bearing axes displaced from the platform rotation axes.
2. Discussion of the Related Art
Current motion platforms are capable of moving a human-sized payload in multiple degrees of freedom. These types of platforms include Stewart platforms, Gough platforms and parallel link systems. Further, U.S. Pat. No. 5,431,569 (Simpkins et al) discloses a motion simulator that uses an existing personal computer and off the shelf software to physically simulate and control the motions of a computer generated vehicle. The motion simulator is manually powered by the user and includes a control stick connected to a computer input, whereby control stick movement is translated into movement of the computer generated vehicle. A rigid control arm connects the control stick to a base unit and to a cockpit frame to move the cockpit frame relative to the base unit as the control stick is moved. The center of gravity of the cockpit is located below the pitch and roll axes so the cockpit tends to return to an initial position.
U.S. Pat. No. 6,330,837 (Charles et al) discloses a parallel mechanism capable of positioning and orienting an end platform with up to six or more degrees of freedom. The mechanism includes six links having first and second ends. The first end is connected to an end platform for supporting a tool, while the second end is connected to an actuator capable of translating the second end. A rotational drive mechanism may be provided for rotating an object mounted on the end platform at varying orientations of the end platform independently of movement of the end platform as a whole.
U.S. Pat. No. 6,357,827 (Brightbill et al) discloses a device including a two degree-of-freedom pivot supporting a platform. In particular, this patent discloses a portable seat including one or more moving seating assemblies. A motion mechanism provides each seating assembly with at least one of total rocking, vertical, lateral and turning movement. The seating assemblies are provided at a neutral angle that corresponds to the particular seat application, while the amount of rocking and/or vertical movement is based on the neutral angle. The neutral angle orientation, rocking movement and vertical movement in combination cause the weight supported by occupant seat bones, posterior and thighs to be optimally distributed on the seating assembly, thereby improving seating comfort as applied to a given seating environment.
However, the above types of platform systems tend to be large and require external power sources to achieve movement. Further, a majority of the systems, including the Brightbill et al device, are configured where the center of rotation must exist outside of the work envelope (e.g., systems employing a two degree-of-freedom pivot to support a platform). System configurations including a center of rotation within the work envelope, such as a Stewart platform, typically require computer control to move multiple axes and offset the center of rotation to a desired location.
In an attempt to overcome some of the aforementioned problems, the related art provides a gimbal mechanism. The gimbal is compact (e.g., capable of fitting into a small space) and requires low power for actuation. Typically, a chair or other support is attached to a gimbal, where a pitch or horizontal axis is perpendicular to a user or object being manipulated, while a roll axis is aligned with the user or object orientation. Since the gimbal axes may be arranged to traverse a center of mass, the system may be balanced to achieve movement with reduced power. For example, U.S. Pat. No. 6,037,927 (Rosenberg) discloses an apparatus for interfacing movement of a shaft with a computer. The apparatus includes a support, a gimbal mechanism having two degrees of freedom, and three electromechanical transducers. The gimbal mechanism has a base portion rotatably coupled to the support to provide a first degree of freedom and an object receiving portion rotatably coupled to the base portion to provide a second degree of freedom. A first electromechanical transducer is coupled between the support and base portion, a second electromechanical transducer is coupled between the base portion and object receiving portion, and a third electromechanical transducer is coupled between the object receiving portion and an elongated object that is at least partially disposed within the object receiving portion. When a shaft is engaged with the gimbal mechanism, the shaft can move in three degrees of freedom in a spherical coordinate space, where each degree of freedom is sensed by one of the three transducers. A fourth transducer can be used to sense rotation of the shaft about an axis.
The gimbal type mechanism suffers from several disadvantages with respect to human sized payloads. In particular, gimbal ergonomics typically require both pitch and roll axes to be supported on one side, thereby producing a significantly cantilevered system. This tends to result in either a massively overbuilt frame or an excessively springy or bouncy mechanism.